WARNING: The following contains spoilers for Batman: The Long Halloween Special #1, on sale now from DC Comics.
One of the most celebrated Batman comic book stories of all time is Jeph Loeb and Tim Sale's 1996 maxi-series Batman: The Long Halloween. To celebrate its 25th anniversary this year and its two-part animated feature film adaptation, Loeb and Sale have returned to the fan-favorite story they began and crafted an epilogue of sorts to tie up The Long Halloween's longstanding loose ends as the Dark Knight and Commissioner Jim Gordon remain haunted by the legacy of the Holiday Killer. And by the time this denouement reaches its conclusion, it appears to solve The Long Halloween's grand, overarching mystery while putting its characters at another crossroads.
The original Long Halloween followed a year-long murder mystery with a shadowy serial killer striking on a different holiday each month, gunning down those connected to the Falcone crime syndicate while a young Batman dealt with the rise of his rogues' gallery. While Batman and Gordon initially believed Alberto Falcone and Harvey Dent -- after his recent transformation into Two-Face -- were the two killers, The Long Halloween's twist ending revealed that Harvey's wife Gilda Dent was the first Holiday Killer, murdering Falcone's associates after seeing the toll the syndicate was taking on her husband. However, Batman was unaware of this, with Loeb and Sale's sequel story Batman: Dark Victory revealing that Gilda had since escaped justice and left Gotham City sometime prior.
Batman: The Long Halloween Special #1 -- by Loeb, Sale, Brennan Wagner and Richard Starkings -- takes place sometime after the events of Dark Victory, which saw Alberto's sister Sofia become a copycat killer striking on holidays under the serial killer moniker The Hangman. With Two-Face on the loose once again, along with the other holiday-based supervillain Calendar Man, Batman and Gordon openly ponder if they ever really knew their old friend before he descended into madness and villainy. This contemplation is put to a premature end when Calendar Man and his gang target Gilda as revenge for using the holiday-based gimmick as a criminal calling card better than he ever could. With this plot, Julian Day evidently confirms his knowledge of Gilda's murderous secret as the original Holiday Killer.
The Calendar Man was one of the big, perhaps unrealized aspects of the original Long Halloween, with Batman and Gordon attempting to question Day about Holiday's identity and where the killer would strike next only to be given esoteric riddles and nonsense at every turn. Calendar Man was similarly incensed that Two-Face opted to leave him in Arkham Asylum rather than have him join in on the showdown against Carmine Falcone and Batman, further underscoring his grudge against the Dent family upon his eventual escape during the special.
However, the resolution to one of The Long Halloween's dangling plot threads comes at the very end of the special, with Batman realizing that the reason Calendar Man targeted Gilda specifically wasn't necessarily to get back at Two-Face but because Gilda was Holiday herself. While not fully articulated by Batman, as he and Gordon compare notes over their recent foiling of the Calendar Man's plot, it is heavily implied that the World's Greatest Detective has figured out Gilda's bloody secret as she and Two-Face depart for parts unknown, leaving the Holiday Killer on the loose once again, albeit on the run this time.